APPENDIX. 47 



water, are held together by: (i) The attraction of the 

 micellae for each other, which varies inversely as the square 

 of the distance. (2) The attraction of the micellae for water, 

 which varies inversely as some higher power of the distance. 

 (3) The force which holds together the ultimate chemical 

 molecules of which each micella consists. 



"Since the swelling up of organized bodies does not take 

 place equally in all three dimensions of space, and on account 

 of their double refraction, Nageli inferred that in form the 

 micellae are crystals, probably parallelopipedal, with rectang- 

 ular or rhomboidal bases." 



The law that ''bodies attract each other with a 

 force which varies inversely as the square of the 

 distance, ' ' has been proven only in its application 

 to the heavenly bodies. Nageli has applied this law 

 to molecules, unsupported, however, by any evi- 

 dence other than that of analogy. On the other 

 hand, there is evidence that molecules do not invari- 

 ably act according to this law. 



Spontaneous generation (p. 4) was an important 

 item in Nageli 's doctrine, and might almost be said 

 to be fundamental to it, although it is 7iot really 

 necessary to the internal perfecting principle, which 

 may be regarded as the chief feature of the Median- 

 ico-Physiological Theory. Up to 1865 Nageli believed 

 in the spontaneous origin of many fungi, and thought 

 that it could be demonstrated. He was obliged to 

 abandon the experimental evidence, but to the close 

 of his life held the views of abiogenesis presented 

 in the accompanying translation. 



The characteristic and most interesting feature 

 of the Mechanico-Physiological Theory is certainly 

 Nageli's conception of an automatic perfecting prin- 

 ciple (Autonome Vervollkommnung). This concep- 

 tion may be briefly outlined as follows: 



